Roll and press gas lighters are commonly used for lighting cigarettes. They comprise a gas reservoir, a gas regulation system including a valve opened and closed by a lever, a flint, and a wheel assembly. The wheel assembly preferably comprises a sparkwheel disposed between two thumbwheels of larger diameter than the sparkwheel. The sparkwheel rubs frictionally against the flint when rotated, in order to project sparks above the opened burner and so ignite the gas, producing a flame. Such lighters traditionally include a windshield around the fuel jet, often with a tongue passing over the sparkwheel in order to avoid the user's thumb becoming soiled with flint dust. Many modern lighters also include this feature.
It is important to prevent the use of such lighters by children under the age of 5 years. The standard for child resistance has been specified in the USA by means of a functional test by the Consumer Product Safety Commission: 16 CFR Parts 1145 and 1210, Risks of Injury Associated with Lighters That Can Be Operated by Children; Safety Standard for Cigarette Lighters; Rules: Federal Register, Monday Jul. 12, 1993. The degree to which a lighter is child resistant may be objectively determined by applying the test described in these Rules and Regulations.
Two main systems are employed to make lighters child resistant. In the more common system, a blocking mechanism adjacent the lever prevents the lever from being moved into the operative position. This mechanism must be manipulated by the user each time the lighter is used, and resets automatically to the blocking position afterwards.
In the other system, the operating characteristics of the lighter are controlled so that while the lighter can be operated more easily, its successful operation is dependent on some quality of the user, such as strength, dexterity, intuition, etc., which is typical of adults but absent in small children.
The latter system is exemplified by FR 95 08011 to the present applicant, which discloses a child resistant lighter whose thumbwheels are provided with smooth peripheral surfaces. In order to engage the thumbwheels and rotate the wheel assembly, the user's thumb must apply more pressure than can be exerted by a child. However, in practice there are limitations inherent in this design.
FR A-2417722 discloses a guard which extends over the sparkwheel to improve the aesthetic appearance and protect the top part of the lighter. It also prevents contact between the user's thumb and the sparkwheel which may cause the thumb to become dirty.
U.S. Pat. No. 5,769,098 to BIC discloses a resilient guard which is mounted around the sparkwheel and projects above the thumbwheels to prevent the user's digit from reaching the wheel assembly. In order to engage the thumbwheels, the user must press hard enough on the guard to depress it.
However, it is found in practice that the protruding guard can cause discomfort for the adult user of the lighter as the pulp of the user's thumb is forced around it.
It is also found in practice that the adult user who experiences difficulty or discomfort in using a lighter will often attempt to remove the safety mechanism which causes the difficulty or discomfort, leaving the lighter vulnerable to use by children.